1. Field
The present invention relates generally to communications, and more specifically, to systems and techniques for supporting international dialing while roaming across multiple network platforms in a wireless communications system.
2. Background
Roaming refers to the ability to make and receive calls outside of a user's home network. More specifically, international roaming is the ability make and receive calls from a foreign country, using the user's own handset and the foreign country's wireless network. Typically, international roaming requires a user to dial an international access code to reach a telephone number outside of the country where the user is located. International access codes are specific to each country and, in some cases, to the carrier whose network supports the call. For example, a user in the United States must dial “011” on his handset in order to use the international roaming feature to place an international call. A user in France would dial “00,” “40,” or “70,” or another international access code, depending on which carrier he chooses to utilize, in order to place an international call from France. Users who frequently travel must keep track of a variety of different international access codes in order to use their handsets to make phone calls in different countries. Because many countries have different international access codes, and because the international access codes within a single country may vary according to carrier, accurate knowledge of the codes may be a significant burden on travelers.
The “+ Code” Dialing Feature
A feature, sometimes referred to as the “+ code” dialing feature, enables international dialing in a cellular system. The Global System for Mobile Communications (GSM) standard for wireless networks supports a version of this international dialing feature in which users may dial a (+) key on their handset in lieu of dialing the international access code. Dialing the (+) key marks the call as an international call, instructing the local switching system to route the call to an international switch. The “+” indicator means the dialed digit string is an international number. For example, with + code dialing, a subscriber making an international call can dial “+CountryCode-AreaCode-Customer Number”. According to this approach, the handset translates the “+” code into “international number type”, the network recognizes the “international number type” and routes the call to international gateway, if the country code (CC) in the dialed number is different from the area of operation. By contrast, if the dialed digit string begins with the country code of the current serving system, then the network (MSC) should remove the CC from dialed number and set up the call as a local or national call.
To illustrate how some of these terms are commonly used, some examples will now be provided. When placing a call to a given phone number, the phone number dialed by a user can be in several different formats depending upon where the user is located and what network the user is calling from. For example, assume three callers located in different regions of the world would like to call someone in San Diego who has a customer/local number 658-2598. Further assume that the first caller is located in San Diego in a region with the same area code, the second caller is located in the United States but outside San Diego, and the third caller is located outside the United States, for instance, in China.
The first caller can simply dial the customer number or local number, 658-2598. If the first caller is still in San Diego, but calls from a region with a different area code the first caller might need to dial 858-658-2598, where the digits “858” are the area code. The second caller would have to dial 1-858-658-2598, where the digit ‘1’ is the national access code, the digits “858” are the area code, and the digits “658-2598” are the customer number or local number. This is also known as a “long-distance” call. The third caller would have to dial 00-1-858-658-2598, where the digits “00” are international access code, the digit “1” is the country code for the United States (as opposed to the national access code in the preceding example), the digits “858” are the area code, and the digits “658-2598” are the customer number or local number. This call will be routed to an international gateway and then directed to the USA. Accordingly, with an international call, before the user dials the number, the user must know where they are making the call, and the international access code.
To help eliminate the need to know this information, in some networks, a feature known as enhanced international dialing can be used to simplify the dialing. According to this feature, all numbers can be expressed in the format “+ country code-area code-customer number), where “+” means the number is an international number type. The digits after + are the “country code”. Thus, in the example above, the third caller can simply dial +1-858-658-2598, and does not need to know the international access.code.
Unfortunately, users whose handsets include the GSM-supported (+) key cannot utilize this function in areas that are not covered by a GSM network. If a mobile user dials a national call with international number type, some systems cannot correctly analyze the number to set up the call. For example, all code division multiple access (CDMA) systems do not support a + code dialing feature and do not recognize or support the mark accompanied by a call that has been placed with a (+) key, and therefore cannot route the call to an international switch. Instead, in order to route an international call, CDMA systems require the appropriate international access code to accompany the call. For example, a CDMA user typically must dial “IAC-CC-AC-CustomerNumber” to make international call, and the network routes the call to international gateway after recognizing the IAC. This requires that CDMA subscribers know the International Access Code (IAC) to make international calls and the National Access Code (NAC) to make national calls when roaming to other countries.
There has recently been an increasing demand for simplified access procedures when roaming internationally. To help alleviate these issues, patent application Ser. No. 10/315,673 entitled “International Dialing In Cellular Networks” filed Dec. 9, 2002, assigned to the assignee hereof and hereby expressly incorporated by reference herein, describes, among other things, an automated international dialing feature. This feature allows users to engage in international roaming, regardless of the network supporting the call, without knowing and entering the proper international access code.
Operators appreciate that Standard +code dialing will require roaming partners' to upgrade their networks to support this feature. These upgrades may not be deployed until some future time. In the interim, there is a need in the art for enhanced international dialing features that can help alleviate this problem. It would be desirable if such a feature could be implemented without the need to upgrade the serving networks.